There are various reasons for logging writes made to a data file on a storage medium. One of those reasons is write monitor differencing. Write monitor differencing is a method for synchronizing and backing up data by making changes to a previous backup based on writes to the storage medium since the previous backup. As only the writes since the previous backup are required to perform a new backup, backup time is reduced.
Typically, write difference monitor log files are arranged as a series of write entries according to the respective time of each write. This serial arrangement introduces a number of issues. For example, if there are multiple writes to the same location then all but the latest write record to that location in the log file becomes redundant. Sorting out the previous write records from the log file can be problematic. Additionally, the log file can potentially become very large as the time between backups increases and that further compounds the aforementioned previous writes to the same location issue. A large log file size will also typically increase the time required to perform a backup since write monitor differencing is a sequential backup methodology.